1. Field of the Invention
This invention relates to a method for sliding a seal with a lip, such as an oil seal or G seal, onto a shaft, a method for recovering the curl of the lip occurring when the seal is slid onto the shaft, and an apparatus for sliding the seal onto the shaft.
2. Description of the Related Art
Conventionally, a seal with a funnel-shaped lip is known. The lip projects toward the inner circumference of an annular body of the seal. In this seal, the end of the lip which is formed of an elastic member, such as rubber, is in direct contact with a shaft, so that the content (oil or powder) inside the seal can be prevented from leaking outside and, at the same time, foreign objects (dust or the like) can be prevented from invading inside of the seal from the outside.
When the seal is slid onto the cylindrical shaft, which is a corresponding part to be incorporated with the seal, in a state in which the front end of the lip is directed toward the shaft, there is a case in which the lip is turned inward or is curled inside of the seal. This case makes it impossible to prevent the leakage of the content to the outside and prevent the invasion of the foreign objects through the seal.
For this reason, an apparatus has been proposed for sliding a seal with a lip onto a shaft without inverting or curling the lip in such a way that a pipe-like member is inserted in the seal in advance and, in this state, the seal is slid onto the shaft and thereafter the pipe-like member is pulled away from the seal (see Japanese Utility Model Application Early Laid-Open Publication No. Hei 4-76331, for example). Also, a seal with a lip has been proposed which is provided with a spring for pressing the seal so as not to curl the lip when sliding the seal onto a shaft (see Japanese Utility Model Application Early Laid-Open Publication No. Hei 6-30565, for example).
There is also a method for detecting whether a lip of a seal has been curled. For example, in Japanese Registered Utility Model No. 3007446, a method is proposed which includes the steps of forming a notch in the circumferential edge of a seal with a lip and making an air-leakage test in order to easily detect whether the lip of the seal has been curled.
In the aforementioned apparatus disclosed by Japanese Utility Model Application Early Laid-Open Publication No. Hei 4-76331, a mechanism for inserting the pipe-like member into the seal is also required in addition to a mechanism for sliding the seal onto the shaft. Therefore, disadvantageously, the apparatus requires a larger space, and an inserting operation must be carried out twice. As a result, the structure of the apparatus becomes complicated. In the aforementioned seal disclosed by Japanese Utility Model Application Early Laid-Open Publication No. Hei 6-30565, the seal is provided with an annular portion to which a garter spring is attached to prevent the lip from curling. This makes the structure of the seal unique and complicated.
In the aforementioned method disclosed by Japanese Registered Utility Model No. 3007446, a device for supplying air is inevitably required to make the air-leakage test. As a result, large-sized assembly equipment is required, and thus equipment costs are raised.
Further, the prior art methods and apparatus mentioned above are each proposed from only the viewpoint of sliding the seal onto the shaft so that the lip is not turned inward or is not curled. In other words, the methods and apparatus pay no attention to uncurling the lip which has been curled.